It is well known to those skilled in the art that nonionic surfactants are useful in formulating laundry detergents for use in low water temperature washes. It is further known that nonionic surfactants are particularly efficient at removing oily soils from synthetic fabrics but that they are not as efficient at removing particulate soils as anionic surfactants. As a result it is desirable to include detergent builders in detergent formulations containing nonionic surfactants to improve performance on particulate soils and provide good overall cleaning performance. However, the amount of nonionic surfactant that can be included in powder detergents is limited by the amount that can be absorbed into or adsorbed onto the solid components. Agglomeration techniques usually produce dense particles that have little capacity for absorbing nonionic surfactants and the final compositions usually have poor solubility rates and flowability. Spray-drying techniques produce more porous particles that can sorb more nonionic surfactant. However, the temperatures involved in spray-drying can cause oxidation of the nonionic surfactant and it is desirable to add the nonionic surfactant in a second step if a high concentration is desired. Since the spray-drying process is energy and capital intensive, this approach results in high manufacturing costs. In addition, if certain builders are present, the spray-drying process itself can lead to the formation of insoluble particles that deposit on clothes during the washing process.
High levels of nonionic surfactants can be readily incorporated into liquid laundry detergents. However, these formulations are normally severely limited in the type and amount of builder that can be incorporated therein since the builder must be soluble or dispersible in the formulation to prevent phase separation. As a result, the overall particulate soil removal performance of liquid laundry detergents is generally poorer than that of powder detergents.
U.S. Pat. No. 4,316,812, issued to Hancock et al, appears to disclose liquid detergent compositions containing builders, a bleach, and a nonionic surfactant system, in which the solids have an average particle diameter of less than 10 microns and the nonionic surfactant system has a pour point of less than 10.degree. C. However, it is expensive and inconvenient to use most conventional builders and most other solids at such a small particle size and a potential for the development of health and safety problems related to dusting with these builders and solids exists. Post milling the composition to reduce the particle size of the solids may eliminate the health and safety problems, but it requires an extra processing step that is energy intensive, and it generates significant heat which may affect temperature-sensitive compounds of the composition. Furthermore it may have a deleterious effect on encapsulated materials within the composition. Furthermore, no mention is made of the solubility characteristics of these formulations in cold water.
There have been attempts to combine high levels of nonionic surfactants and builders in laundry detergent formulations which have the physical form of mulls or pastes. U.S. Pat. No. 4,264,466, issued to Carleton et al, describes detergent mulls which contain chain structure clays to prevent phase separation of the liquid and solid components. U.S. Pat. No. 4,409,136, issued to Cheng, discloses a paste detergent composition containing a specific nonionic surfactant along with a relatively high amount of water.
Because of the viscous nature of these paste formulations, it is difficult to deliver them into the washing machine from a conventional, liquid laundry detergent bottle, even one equipped with a pump dispenser. The use of a squeezable tube, similar to those used to dispense toothpaste, to dispense a liquid detergent in the form of a paste may be feasible from a technical consideration, but the size of the tube required to contain a reasonable amount of detergent for multiple wash loads would make it difficult for the consumer to use conveniently.
The use of pouches constructed of water soluble films to deliver unit dosages of laundry additives is well documented. However, there has been no demonstration in the prior art of the use of such pouches to contain and deliver a composition containing a high level of nonionic surfactant. For example, U.S. Pat. No. 4,115,292, issued to Richardson et al, shows compositions with low amounts of very high pour point nonionic surfactants and relatively high amounts of water in water-soluble polyvinyl alcohol pouches.